Cut each grape 3/4 through from stem end.
Pat grapes dry with paper towels.
Beat butter in processor or small bowl of electric mixer until creamy.
Add cheese and beat until thoroughly blended.
Spoon mixture into pastry bag fitted with small star tip and refrigerate until firm.
Pipe some of mixture into center of grape, carefully pressing sides together.
Gendy transfer to tray.
Repeat with remaining grapes.
Chill until firm.
Just before serving, arrange grape or lemon leaves on platter and top with stuffed grapes.
Grapes can be prepared 1 day ahead.